Dual scara arm

ABSTRACT

A substrate transport apparatus having a drive section and a scara arm operably connected to the drive section to move the scara arm. The scara arm has an upper arm and at least one forearm. The forearm is movably mounted to the upper arm and capable of holding a substrate thereon. The upper arm is substantially rigid and is adjustable for changing a predetermined dimension of the upper arm.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a divisional of U.S. patent application Ser. No.11/148,871, filed Jun. 9, 2005 (now U.S. Pat. No. 8,376,685) and claimsthe benefit of U.S. Provisional Application No. 60/578,571, filed Jun.9, 2004 which are incorporated by reference herein in its entirety.

BACKGROUND

1. Field of the Invention

The present invention relates to a substrate transport apparatus.

2. Brief Description of Related Developments

The continuous demand by consumers for ever cheaper electronic deviceshas maintained pressure on manufacturers of the device to improveefficiency. Indeed, in the current market place, many of the devices,and to a much greater extent in the electronic and semiconductorcomponents, used in the devices, have become commodities. The desire ofmanufacturers of electronic and semiconductor device to increaseefficiency manifests itself at all levels, but is of specialsignificance in the design, construction, and operation of fabricationfacilities or fabs. One unit by which to measure the efficiency of agiven fab may be the throughput per unit of area (e.g. throughput perFT2). As may be realized from this unit of measure, the fab efficiencymay be increased by raising the production rate per. fabrication tool orwork station of given size (space/footprint envelope), or reducing thesize of the work station used to generate a greater work station densitywithin the fab. Thus, numerous efforts have been made to increaseproduction rates. A number of these efforts have involved providingtransport apparatus capable of providing faster swap times (i.e. thetime period involved in removing a workpiece from a processing moduleand replacing it with a new workpiece). Other efforts have been directedat reducing the overall footprint of the fabrication tool. As may berealized, there are constraints that operate against, these efforts toimprove fab efficiency that intrinsically arise from the fabricationsystem itself. For instance, fabricators currently favor fabricationsystem configurations for batch processing of 200 mm and 30 mm wafersthat employ a general radial tool layout. This in turn defines thisextension of the transport apparatus, to transport wafers to thedifferent tool modules, which in turn impacts the overall footprint ofthe transport apparatus. As may be realized, in conventional transportapparatus, the longer the reach, the larger the footprint (e.g. longerlinks on transport elements are used to accommodate a longer reach). Anexample of a conventional transport apparatus is described in U.S. Pat.No. 6,669,434. This conventional apparatus is a double arm substratetransport unit that has a base arm and first and second forearmssupported from the same end/tip of the base arm. Though providing afairly compact overall footprint, this conventional transport apparatussuffers longer swap, times due in part, to the dynamic effects ofmounting both forearms on one end of the base arm (e.g. increased polarmoment of inertia, substrate transport speed during extension/retractionof arm at snap out does not have benefit or base arm motion). Thepresent invention as incorporated in the exemplary embodiments overcomesthe problems of the conventional transport apparatus as will bedescribed in greater detail below.

SUMMARY OF THE INVENTION

In accordance with one exemplary embodiment, a substrate transportapparatus is provided. The apparatus comprises a drive section, and ascara arm. The scara arm is operably connected to the drive section tomove the scara arm. The scara arm comprises an upper arm and at leastone forearm movably mounted on the upper arm and capable of holding asubstrate thereon. The upper arm is a substantially rigid link that isadjustable for changing a. predetermined dimension of the upper arm.

In accordance with another exemplary embodiment, a substrate transportapparatus is provided. The apparatus comprises a drive section and ascara arm. The scara arm is operably connected to the drive section tomove the scara arm. The scara arm has an upper arm and at least oneforearm. The forearm is movably mounted on the upper arm and capable ofholding a substrate thereon. The upper arm is substantially rigid havinga first substantially rigid arm section releasably attached to a secondsubstantially rigid arm section. When released the first arm section ismovable relative to the second arm section for changing a predetermineddimension of the upper arm.

In accordance with yet another exemplary embodiment, a substratetransport apparatus is provided. The apparatus comprises a drive sectionand a scara arm. The scara arm is movably connected, to the drivesection. The scara arm comprises an upper arm, a first forearm, and asecond forearm. The upper arm is pivotably joined to the drive sectionto rotate about a first axis of rotation relative to the drive section.The upper arm is an elongated linear member terminating at oppositeends. The upper arm is located relative to the drive section so that thefirst axis of rotation is at one end of the opposite ends of the upperarm. The first forearm has a first end effector depending therefrom. Thefirst forearm is pivotably joined to the upper arm at another end of theopposite ends of the upper arm. The joint between the first forearm andthe upper arm defines a first elbow joint of the scara arm. The secondforearm has a second end effector depending therefrom. The secondforearm is pivotally joined to the upper arm at the other end of theopposite ends of the upper arm. The joint between the second forearm andthe upper arm defines a second elbow joint of the scara arm. The firstelbow joint and the second elbow joint are independent of each other.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and other features of the present invention areexplained in the following description, taken in connection with theaccompanying drawings, wherein:

FIG. 1 is a schematic perspective view of a substrate transportapparatus incorporating features of the present invention in accordancewith an exemplary embodiment;

FIG. 2 is a cross-section view of the substrate transport apparatus inFIG. 1;

FIG. 3 is an enlarged partial cross-section view of a drive section ofthe transport apparatus in FIG. 1;

FIGS. 4-4A respectively are a main plan view of the transport apparatusand a secondary plan view of the upper arm of the transport apparatus(the forearms and end effectors in this view being omitted for clarity)and showing a footprint of the transport apparatus with the upper arm ofthe apparatus placed in a first configuration;

FIGS. 5-5A respectively are a another main plan view of the transportapparatus and another secondary plan view of the upper arm of thetransport apparatus (the forearms and end effectors in this view againbeing omitted for clarity) with the upper arm of the apparatus placed inanother configuration;

FIGS. 6-6A respectively are a yet another main plan view of thetransport apparatus and yet another secondary plan view of the upper armof the transport apparatus (the forearms and end effectors in this viewyet again being omitted for clarity) with the upper arm of the apparatusplaced in yet another configuration;

FIG. 7 is a schematic cross-section view of a substrate transportapparatus in accordance with another exemplary embodiment;

FIG. 8 is a schematic plan view of a transport apparatus in accordancewith another exemplary embodiment, the apparatus being shown in anextended position;

FIG. 9 is another schematic plan view of the apparatus in FIG. 8 showingthe apparatus in a retracted to a register position, and showing afootprint perimeter of the retracted apparatus;

FIG. 10 is a schematic cross section view of the substrate transportapparatus in FIG. 8;

FIG. 10A is a partial schematic elevation view of one end of thesubstrate transport apparatus in accordance with another exemplaryembodiment;

FIG. 11 is a partial cross sectional view of the upper arm and forearmsof the substrate transport apparatus in accordance with still anotherexemplary embodiment; and

FIG. 12 is a schematic view of a portion of a transport apparatus inaccordance with an exemplary embodiment.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENT(S)

Referring to FIG. 1, a perspective view is provided of a substratetransport apparatus 10 incorporating features of the present invention,in accordance with one exemplary embodiment. Although the presentinvention will be described with reference to the embodiment shown inthe drawings, it should be understood that the present invention can beembodied in many alternate forms of embodiments. In addition, anysuitable size, shape or type of elements or materials could be used.

In FIG. 1, the substrate transport apparatus 10 is shown being used totransport semiconductor wafers S, such as 200 mm or 300 mm wafers, forexample purposes. The transport apparatus, in accordance with theexemplary embodiments described herein, however may be suitablyconfigured to handle any desired flat workpiece items including the 200mm or 300 mm semiconductor wafers (already mentioned), semiconductorpackaging substrates (such as high density interconnects HOI),semiconductor processing imaging plates (e.g. masks or reticles) andsubstrates for flat panel displays. The apparatus 10 is also shown inFIG. 1 as being located within a generally illustrated transport chamberP (schematically shown in phantom) of a processing or workstation (notshown). As may be realized the transport chamber P provides a free/openspace envelope in which the apparatus 10 can be articulated to transportthe substrates S between an origin and a destination. The size of thetransport chamber is dependent, at least in any part, on the footprintof the transport apparatus, and apparatus 10 in accordance with thefeatures of the exemplary embodiment allows the size of the chamber P tobe minimized for a given reach of the transport apparatus as will bedescribed further below. The transport chamber P in this embodiment maybe located in an environmental portion of a workstation, or may be partof the atmospherically controlled or isolated section of theworkstation. For example, the transport chamber P may be part of theenvironmental front end module of a workstation. In that case, thetransport apparatus 10 may be used for moving substrates S through thetransport chamber from loading station (e.g. a load port) (not shown) toa load lock, or processing module (not shown) and vice versa. In thecase where the transport chamber P is located within the atmosphericallycontrolled section of a workstation, the transport apparatus 10 may beused to transfer substrates between the load locks (isolating thecontrolled atmosphere in the atmospherically controlled section from theenvironmental section or other atmospherically controlled sections withdifferent atmosphere) and substrate processing chambers (not shown) suchas material deposition, etching, masking, lithography, heating chambersfor example. The apparatus 10 in accordance with the exemplaryembodiments described herein, operates equally well whether in anenvironmental transport chamber or atmospherically controlled (e.g.vacuum, inert gas, N2) chamber. The transport apparatus 10 may be fixedin the chamber P or may be mounted on a movable car or shuttle (notshown) such as the example described in U.S. Pat. No. 6,139,245, whichis incorporated by reference herein in its entirety.

Still referring to FIG. 1, the substrate transport apparatus 10generally comprises a drive section 30 and a movable arm assembly 36.The arm assembly 36 has, what shall be referred to generally, as abutterfly scara arm arrangement terminating in two end effectors 38, 39.The arm assembly 36 includes an upper or base arm 66, and two forearms74, 106 depending from opposite ends 66R, 66L of the upper arm. The armassembly 36 is connected to the drive section 30, at shoulder joint 35,(see FIG. 2), to rotate (in the direction indicted by arrow θ in FIG. 1)and extend/retract (in the direction indicated by arrow R) the endeffectors 38, 39 on the arm assembly in order to position substratesinto or pick substrates from any desired module (not shown) having anydesired position on the chamber P. The upper arm 66 is adjustable toprovide the transport apparatus 10 with a minimum footprint whilemaintaining the end effectors 38, 39 in an optimum position (to reduceswap times) as will be described in general detail below.

Referring now also to FIGS. 2 and 3, respectively showing a crosssectional view and an enlarged, partial cross sectional view of theapparatus 10, the drive section 30 may include a vertical drive (notshown) and a rotational drive 34. The vertical drive is capable ofraising and lowering the apparatus 10 along the vertical axis Z (seeFIG. 1). Any suitable type of vertical movement system may be used. Asuitable example is disclosed in U.S. Pat. No. 5,894,760, which isincorporated by reference herein in its entirety. In alternateembodiments, the drive section of the transport apparatus may not have avertical drive. In the embodiment shown in FIGS. 2-3, the rotationaldrive 34 has motors for independently moving the upper arm 66 and eachof the forearms 74, 106. In alternate embodiments, the rotational drivemay have more or fewer motors. In this embodiment, the rotational drive34 is located at the shoulder or base joint 35 where the upper arm 66 ispivotally connected to the frame casing of the drive section. Inalternate embodiments, the rotational drive may be located at any othersuitable location. The rotational drive 34 generally comprises a driveshaft assembly 41 and three motors 42, 44, 46. In an alternateembodiment the drive could have more than three motors. The drive shaftassembly 41 has three drive shafts 50 a, 50 b, 50 c. In an alternateembodiment more than three drive shafts could be provided. The firstmotor comprises a stator 48 a and a rotor 60 a connected to the middleshaft 50 a. The second motor 44 comprises a stator 48 b and a rotor 60 bconnected to the outer shaft 50 b. The third motor 46 comprises a stator48 c and rotor 60 c connected to the inner shaft 50 c. The three stators48 a, 48 b, 48 c are stationarily attached to the tube 52 at differentvertical heights or locations along the tube. In this embodiment thefirst stator 48 a is the middle stator, the second stator 48 b is thetop stator and the third stator 48 c is the bottom stator. Each statorgenerally comprises an electromagnetic coil. The three shafts 50 a, 50b, and 50 c are arranged as coaxial shafts about common axis of rotationD at the shoulder joint 35 of the apparatus. The three rotors 60 a, 60b, 60 c may be comprised of permanent magnets, but may alternativelycomprise a magnetic induction rotor which does not have permanentmagnets. Sleeves 62 may be located between the rotor 60 and the stators48 to allow the robot 24 to be useable in a vacuum environment with thedrive shaft assembly 41 being located in a vacuum environment and thestators 48 being located outside of the vacuum environment. However, thesleeves 62 need not be provided if the robot 24 is only intended for usein an atmospheric environment.

The third shaft 50 c is the inner shaft and extends from the bottomstator 48 c. The inner shaft has the third rotor 60 c aligned with thebottom stator 48 c. The middle shaft 50 a extends upward from the middlestator 48 a. The middle shaft has the first rotor 60 a aligned with thefirst stator 48 a. The outer shaft 50 b extends upward from the topstator 48 b. The outer shaft has the second rotor 60 b aligned with theupper stator 48 b. Various bearings are provided about the shafts 50 andthe tube 52 to allow each shaft to be independently rotatable relativeto each other and the tube 52. In this embodiment each shaft 50 isprovided with a position sensor 64. The position sensors 64 are used tosignal the controller 11 (see FIG. 1) of the rotational position of theshafts 50 relative to each other and/or relative to the tube 52. Anysuitable sensor could be used, such as optical or induction.

Referring still to FIGS. 2 and 3, the arm assembly 36, as noted before,generally comprises upper arm 66 and two forearms 74, 106, each carryinga corresponding end effector 38, for holding and transporting substratesS. As also noted before, the upper arm 66 is pivotally mounted to theframe of the rotational drive at shoulder joint 35 so that the arm 66may pivot about common axis of rotation D at the shoulder as will beseen further below. Each forearm 74, 106 is pivotally mounted to theupper arm 66 at opposite ends of the arm. Hence, forearm 74 is pivotablerelative to the upper arm about elbow joint axis of rotation F, andforearm 106 is pivotable relative to the upper arm about the axis ofrotation E at the opposite elbow joint. As seen in FIG. 2, the armassembly 36 also includes a number of transmission mechanisms connectingthe drives of the rotational drive 34 to the forearms 74, 108 and theend effectors 38, 39 to the upper arm 66.

As seen best in FIG. 2, the upper arm 66 in this embodiment generallyhas two opposing arm sections 72, 78. The sections 72, 78 are joined toeach other, in this embodiment at the shoulder joint 35 of the armassembly. The sections 72, 78 are capable of being locked to each other,allowing the upper arm 66 to be rotated as a unit about shoulder axis ofrotation O. The opposing sections 72, 78 may otherwise be unlocked inorder to reposition the opposing sections relative to each other. Inalternate embodiments, the upper arm may comprise any desired number ofsections, or may be one piece with a lockable flexible joint to allowadjustable positioning of different parts of the section relative toeach other. In this embodiment, the upper arm sections 72, 78 aregenerally similar to each other and hence will be described withreference specifically to section 72 except where different. Upper armsection 72 generally has a hollow frame or casing capable of housing thetransmission 84 connecting the forearm 74 to the correspondingrotational drive (transmission 116 connects forearm 106 in arm section79). One end 66 L of the upper arm section 72 defines an elbow joint ofthe arm assembly 34. A post 80 is fixed to the frame of arm section 72at this end about which idler member (e.g. pulley) 84I of transmission84 is rotatably mounted (similarly idler member 116I of transmission 116is mounted to post 80L in the opposite arm section 78) to provide amotive means to the forearm 74. In this embodiment, the upper armsection 72 is fixedly attached to the outer shaft 50 b of the rotationaldrive 34 (see FIG. 3). The opposing upper arm section 78 is also fixedto the outer shaft 50 b, but in this embodiment, the section 78 isadjustably fixed to the outer shaft 50 b by adjustable attachment orcoupling to the upper arm section 72. As seen in FIG. 3, the upper armsection 72 includes a mounting surface 72M fastened (though fastenersare shown in this embodiment, engagement may be by any suitable torquetransfer system) directly to the outer shaft 50 b of the rotationaldrive. Upper arm section 72 also has a mounting section 72S to which theopposing upper arm section 78 may be adjustably attached as will bedescribed in greater detail below.

As seen in FIGS. 2 and 3, in this embodiment the opposing sections 72,78 of the upper arm assembly 66 are vertically offset. In alternateembodiments, the adjustably positionable section may be positioned inany desired configuration relative to each other, such as being atsubstantially the same vertical level. The mounting or coupling section72S of main section 72 in this embodiment is formed by the frame 73 ofthe arm section. The frame 73 in this embodiment extends around theco-axial shaft assembly of the drive section to form a seating surface73S for the opposing arm section 78. The surface 73S, which in thisembodiment is generally in the same plane as the upper surface of thearm section 72, has locating features 73H for both vertical andhorizontal positioning of the arm section 78 onto arm section 72. Theopposing arm section 78 has a frame 110 that has a mating section 110Swhich is generally conformally configured, with respect to mountingsection 72S so that mating section 110S may be mounted on the mountingsection 72S. In this embodiment the locating features 73H are fastenerholes formed in seating surface 73S. Similarly, the seating surface ofthe mating section 110S of the opposing upper arm section 78 also hasfastener holes 110H. As will be described below, the fastener holesformed in the respective seating surfaces are distributed and spaces toprovide desired indexing positions for indexing the arm section 72, 78relative to each other. Fasteners 75, such as cap screws, bolts,locating pins, may be inserted through holes 110H of the upper armsection 78, into matching holes 73H of the other upper arm section 72thereby locking the two arm sections 72, 78 of the upper arm to eachother. The fasteners are sufficient for torque transfer during movementand hence the upper arm section 78 (which is noted before is notdirectly mounted to the outer shaft 50 b of the rotational drive 34)rotates in unison with opposing arm section 72 when arm section 72 isrotated by outer shaft 50 b about common axis of rotation D at theshoulder joint of the arm assembly. In alternate embodiments, any othersuitable enablement features, such as splines, keys/keyways, may be usedfor locating and torque transfer between the opposing arm sections.

The locating holes 73H, 110H are circumferentially equally distributedon the respective frame 73, 110 of the upper arm section 72, 78. Anydesired number of holes may be used to provide the desired incrementaladjustment spacing between the upper arm section 72, 78 will bedescribed below. The number of locating holes in the mounting sections73S, 110S of the arm sections may be different, as one section 73S, 110Smay include only the minimum number of holes for mechanical loads, whilethe mating section would have additional holes for desired positionaladjustment or indexing. For example, if four fasteners 75 are used formechanical attachment, then one mounting section 73S, 110S may have fourmounting holes 73H, 110H and the other mounting section may have eightor ten or any desired number of holes to accommodate adjustment betweenthe arm sections. The mating surfaces 73S, 110S may include additionalengagement features, such as interlocking or interdigitated lips oredges (not shown) that stably hold the arm sections together when thelocking fasteners 75 are removed. Accordingly, the upper arm sections72, 78 may remain self supporting when the fasteners 75 are removed toeffect positional adjustment as will be described below. The engagementfeatures may be provided with suitable sliding surfaces (not shown) toallow sliding motion between arm sections when being positionallyadjusted without generating particulate matter at the sliding surfaces.In this embodiment, the mounting sections 73S, 110S of the upper armsections are shown as being disposed at the shoulder joint 35 (see FIG.2) of the arm assembly. In alternate embodiments, the adjustableconnection between the upper arm sections may be located at any otherposition along the upper arm.

Referring still to FIGS. 2 and 3, the transmission system 84 for forearm74 is operably connected to middle shaft 50A of the rotational drive 34.The transmission system 116 for the forearm 106 is operably connected tothe inner shaft 50C as shown for example in FIG. 3. Forearm transmissionsystems 84, 116 are generally similar, and are illustrated in thisembodiment as being a belt and pulley system for example purposes. Inalternate embodiments, the transmissions linking the forearms to thedrives may be any other suitable transmission such as a crank andconnecting link system, or a gear and screw type of transmission. Inthis embodiment, the transmission systems 84, 116 generally comprisedrive pulleys 70A, 70B (respectively fixed to the center 50A, and inner50C drive shafts). Idler pulley 84I, 116I are rotatably mounted on posts80 in the elbows of the upper arm 66, and are connected by suitablebelts to the drive pulleys. The frames of the forearms 74, 106, whichare mounted with suitable bearings to rotate freely about posts 80, arefixedly joined to the corresponding idler pulleys. Hence, rotation ofshaft 50 a causes rotation of forearm 74 about axis of rotation F, androtation of shaft 50C causes rotation of forearm 106 about axis E. Thetransmission systems 84, 116 may have any desired reduction ratios, andthe embodiment shown in FIG. 2 has a 1:2 reduction for example purposes.As shown in FIG. 2, each forearm 74, 106 in this embodiment, encases asynchronizer system 98, 124 synchronizing the position of the respectiveend effectors 38, 39 to the upper arm 66. In the embodiment shown, thesynchronizer systems 98, 124 are belt and pulley systems for examplepurposes, and any suitable synchronizer system may be used. Thesynchronizer systems include base pulleys fixed onto the posts 80 at theelbows of the upper arm (which as noted before are fixed to therespective frames) 73, 110 of the opposing sections of the upper arm asshown In FIG. 2. Idler pulleys are fixed to the end effectors, and arerotatably supported in the forearms so that the end effectors are freeto rotate, relative to the forearms, about corresponding axis ofrotation G, H (the axis of rotation at the wrist joints of the armassembly). The reduction ratio of the synchronizer is shown for examplepurposes as being 2:1 though any suitable reduction may be used. As seenbest in FIG. 1, the forearm 106 and end effector 39 mounted thereon, areset off sufficiently from the upper arm 66 to allow forearm 74, with endeffector 38 thereon to move freely past forearm 106 when both endeffectors are transporting substrates S (see FIG. 1).

The apparatus 10 may be provided with end effectors of different lengthsin order to tailor the reach of the apparatus as desired. FIGS. 4-6, areplan views respectively showing the arm assembly 36, 36A, 36B of theapparatus 10 with different length end effectors 38, 38A, 38B, 39, 39A,39B. As may be realized, the reach of the apparatus may be increased orreduced to accommodate the different depths, and in particular substratepick/release positions, that may exist in the various processing orholding modules (not shown) communicating with the transport chamber P(see FIG. 1). For example, in the case where a module of longer lengthis connected to the chamber P the end effector has to reach further out(through an opening) of the chamber to position or pick a substratetherefrom. Conversely, in the case where a shorter length module isconnected to the chamber, the apparatus 10 may have a shorter reach topick or place substrates therein. An effective way to provide theapparatus with the desired reach is to use an end effector with a lengthcorresponding to the desired reach. Hence for a longer reach, the armassembly 36 would have longer end effectors, and for shorter reach thearm assembly would have shorter end effectors. The arm assembly 36 ofthe apparatus shown in FIG. 4 has the longer end effectors 38, 39compared to the end effectors 38A, 39A and 38B, 39B (that areprogressively shorter) correspondingly shown in FIGS. 5-6 (i.e. L isgreater than L1 which is greater than L2).

As may be realized, having a longer length end effector in conventionaltransport apparatus result in an increase in the overall footprint.Further, as may be realized, the transfer chamber P of a processing toolmay be manufactured long before a selection is made as to the type andhence size of modules that will be communicating with the particulartransfer chamber P. Accordingly, the transfer chamber P for conventionalsystems is sized to accommodate the largest anticipated footprint of thetransport apparatus (i.e. the one with the longest possible endeffectors). Further, with the transfer chamber built in advance (to suitmaximum apparatus footprint), conventional apparatus with shorter endeffectors may not receive the benefit of the shorter end effectorsbecause the conventional apparatus are positioned in the transferchamber in the same position as if the apparatus had longer endeffectors. With the shorter end effectors of the conventional apparatusnow positioned further from the modules, the swap times are lengthened.

By comparison as seen from FIGS. 4-6, having end effectors 38, 38A, 38B39, 39A, 39B of different lengths on the arm assembly 36 in thisexemplary embodiment, the footprint of the apparatus may be minimizedfor the longest desired reach and still maintain minimum sway timesindependent of the reach of the transport apparatus. Moreover, theapparatus 10 can provide optimum footprint to extension ratios. Theoverall footprint of the apparatus 10, 10A, 10B (each having endeffectors 28, 39, 38A, 39A, 38B, 39B of different length) is identifiedin FIGS. 4-6 by circumferential perimeter C. To define the footprintperimeter of the apparatus 10, 10A, 10B, the common axis of rotation Dat the arm assembly shown has been located at substantially the centerpoint, and the footprint perimeter is established at the minimum radiusfrom the center providing a perimeter that just encompasses all pointsof the apparatus 10, 10A, 10B and substrates S transported thereon. Asmay be realized from FIGS. 4-6, apparatus 10 (shown in FIGS. 4-4A) hasthe longest end effectors 38, 39 (the end effector length L is definedfor example purposes as extending from pivot and at the wrist joint tothe center of the substrate when positioned on the end effector) andhence the longest reach. The minimum possible footprint perimeter C isestablished to encompass apparatus 10, having the longest desired reach,with substrate S thereon. As can be seen from FIGS. 4-6, the footprintperimeter C is the same size for each apparatus 10, 10A, 10B. Hence,footprint perimeter C for the apparatus 10B with the shortest length(L2) end effectors 38B, 39B shown in FIG. 6 is the same size as theminimum footprint C for apparatus 10 with the longest length (L) endeffectors 38, 39 shown in FIG. 4. It is noted, that the arm assembly 36,36A, 36B of the apparatus 10, 10A, 10B respectively shown in FIGS. 4-6is disposed in the register or initial position of the arm assembly. Theinitial position is the position from which the arm assembly is extendedand to which the arm assembly is retracted during substrate transfer. Inthis embodiment, the initial position of the arm assembly is beingdefined for example purposes as the position where both the opposingsections 72, 78, (as well as 72A, 78A in FIG. 5 and 72B, 78B in FIG. 6)of the upper arm 66, and the forearms 74, 106 (as well as 74A, 106A and74B, 106B) are symmetrically positioned relative to the radial axis ofmotion R of the end effector. In alternate embodiments any otherposition may be selected as initial. As seen in FIGS. 4-6, with the armassembly in the register position the end effectors 38, 39, 38A, 39A,38B, 39B of each apparatus may nevertheless be positioned so that theedge of the substrates held by the end effectors 38, 39, 38A, 39A, 39A,39B regardless of length is at the footprint perimeter C of theapparatus. Hence, the register position of the substrates S (i.e. theposition of the substrates S when the arm assembly 36 is in the registerposition) held by the apparatus is independent of the length of the endeffectors.

As illustrated in FIGS. 4-6, in effect, the arm assembly 36 of theapparatus 10 decouples the relationship between substrate registerposition, and the apparatus footprint C, as well as the end effectorlength. Accordingly, a minimum footprint may be provided to theapparatus 10 for a maximum desired end effector length, and the registerposition of the substrates S, and of the end effectors when not holdingsubstrates, may be optimally selected independent of the end effectorlength. In turn, these features of the apparatus 10 according to theexemplary embodiment, have a direct benefit on the design and functionof the workstation that cannot be provided by conventional transportapparatus. For example, the transfer chamber P may be configured toaccommodate the minimum footprint of the apparatus 10 to accommodate thelongest expected end effector lengths. Further, the optimal location ofthe end effector, regardless of its length, with the arm assembly in theregister position, (i.e. maintaining the end effector so that asubstrate S thereon contacts perimeter C) effectively closes undesiredspaces between the register position of the end effector, or substratethereon, and the extended position of the end effector, thereby avoidingincurring a travel distance penalty for the smaller length end effectorsas in conventional apparatus. Accordingly, minimum swap times are alwaysachieved for the minimum apparatus footprint.

Adjustment of the apparatus footprint, and optimal positioning of theend effector is effected as illustrated in FIGS. 4A, 5A and 6A byadjusting the relative angular positions of the opposing sections 72, 73of the adjustable upper arm 66. FIGS. 4A, 5A and 6A respectively showthe sections 72, 78; 72A, 78A; 72B, 78B of the upper arm in threedifferent positions corresponding to the different length end effectors38, 39; 38A, 39A; 38B, 39B shown on the prior assembly in FIGS. 4-6.Thus, in FIG. 4A the upper arm section 72, 78 are positioned to form aninclusive angle α in FIG. 5A the arm section 72A, 79A form inclusiveangle α1, and in FIG. 6A the arm sections 72B, 78B form inclusive angleα2. Angle α2 is more shallow than angle α1 which in turn is more shallowthan angle α. Thus, as seen in FIGS. 4-6 and 4A-6A, the size of theinclusive angle between the upper arm sections is decreased as thelength (L, L, L2) of the end effectors 38B, 39B; 38A, 39A; 38, 39 isincreased. As the inclusive angle between the opposing upper armsections is decreased, the arms sections are rotated further back(opposite the direction of extension), when the arm assembly is in theregistered position. This in turn moves the forearms 74B, 104B; 74A,104A; 74, 104 back when registered, and thereby moves the end effectorsback allowing the longer length end effectors to remain within theminimum footprint of the apparatus. To move the opposing sections 72, 78of the arm assembly, the bolts 75 (see FIG. 3) locking the arm sectionstogether, (or other locking device) are released. This allows one orboth arm section 72, 78 to be pivoted relative to each other about axisof rotation D until the desired inclusive angle α, α1, α2 is achievedbetween the arm sections. The lock bolts 75 are then reintroducedthereby again locking the arm sections to each other in the newposition. After repositioning the upper arm 66, that in turn repositionsthe forearms and end effectors carried by the upper arm, the controller11 is programmed to set the register position of the drive motors 42,44, 46 (see FIG. 2). Teaching/programming transfer movements of thetransport apparatus 10 may then be accomplished in the conventionalmanner except as otherwise noted below.

Extension and retraction of the arm assembly 36 may be effected in thefollowing manner for example. To extend end effector 39, the upper arm66 is rotated clockwise about axis D by motor 44 (driving the outershaft 50B). The forearm 106 supporting end effector 39 is rotatedcounter clockwise, by motor 46 driving inner shaft 50C and transmission116, about axis E. The synchronizer 124 anchored to the upper armmaintains the end effector 39 linearly aligned with radial axis ofmotion R as the end effector is being advanced by the upper arm. Duringtransport operations it may be desired to maintain the other endeffector(s) 38, 39 retracted when one end effector is being extended.Accordingly, for example, if end effector 39 is being extended endeffector 38 may be retracted. To retract end effector 38, when endeffector 39 is being extended, the forearm 74 is also rotated counterclockwise by driving motor 42 driving mid-shaft 50A and transmission 84,about axis F. The motor 42 moves the forearm 74, relative to thepivoting upper arm 66, to maintain the retracted position of the forearm74 as shown in FIGS. 4-6. The synchronizer 98 anchoring the end effector38 to the upper arm maintains the end effector 38 aligned with theradial axis R of extension/retraction. Retraction of the extended endeffector is accomplished in the opposite manner to extension. Duringretraction of extended end effector 39, the end effector 38 ismaintained, at least temporarily, in the retracted position by reverserotations (e.g. clockwise about axis F). To continue extending motion,such as during a substrate swap, of the previously retracted endeffector 38, the upper arm 66 rotation (i.e. counter clockwise,commenced to retract the previously extended effector 39) is maintainedpast the register position, waive rotation of forearms 38 (i.e.clockwise to extend) and 39 (i.e. clockwise to retract and remainretracted during extension of opposing forearm) is continued until thedesired positions are reached.

As noted before, the register position of the arm assembly 68 has beendefined, for purposes of description of this embodiment, as being theposition of the arm assembly when the forearms 74, 106 and upper armsections 72, 78 are symmetrically arranged relative to the radial axis Ralong which the end effectors 38, 39 are extended/retracted (though asnoted before the register position may be selected as any other desiredposition). It may be realized from FIG. 2, that due to the synchronizers98, 124 respectively locking the end effectors 38, 39 to the upper arm,repositioning of the upper arm sections 72, 78 to provide the desiredinclusive angle α, α1, α2(see FIGS. 4A-6A) causes the end effectors 38,39 to be angled relative to teach other in this embodiment. This isschematically illustrated in FIG. 4 by phantom axis 38 CL and 39 CL,that are meant to show the true orientation of the center lines of theend effectors 38, 39 when the upper arm sections 72, 78 are set to forminclusive angle α shown in FIG. 4A. Setting the upper arm sections 72A,78A; 72B, 78B further apart, as shown in FIGS. 5A-6A, rotates the centerlines of the end effectors 38B, 39 towards the radial axis R, reducingthe angle (see FIG. 4) between the end effectors. To accommodate theangle B between the end effectors 38, 39, during swap motion of the armassembly, an additional rotation of the upper arm may be performed toalign the extending end effector with the radial axis R. For example, ifend effector 39 is being extended, the upper arm 66 is rotated to alignend effector center line 39 CL with radial axis R. This additionalmotion may be performed at any desired time prior or during extension.When retracting the end effector 39 during a swap, an additional motionof the upper arm 66 may be performed to bring the centerline 38 CL ofend effector 38 into alignment with radial axis R. In alternateembodiments, an adjustment means may be provided, such as for example arelease mechanism unlocking the synchronizers for the end effectors,from the upper arm. This would allow the upper arm sections to bepositioned as desired while maintaining a desired alignment for the endeffectors relative to radial axis R. After adjustment, the lockingmechanism would be reengaged to again lock the end effectors to theupper arm.

Referring now to FIG. 7, there is shown a cross-section view of asubstrate transport apparatus 110 in accordance with another exemplaryembodiment. The transport apparatus 110 in this embodiment is generallysimilar to the apparatus 10 described before and shown in FIGS. 1-6.Accordingly, similar features between the exemplary embodiments aresimilarly numbered, and will be mentioned only briefly below. As withapparatus 10, there is a drive section 234 and an arm assembly 236. Armassembly 236 has at least one upper arm 266, pivotable about axis D atthe shoulder joint, and two forearms 274, 306 pivotally mounted atopposite ends of the upper arm. The upper arm 266 includes at least twosections 272, 278 with a lockable adjustable interface 273I connectingthe sections to each other. The interface 273I can be locked to hold theupper arm sections in desired orientation relative to each other. Whenunlocked, the interface 273I allows the upper arm sections 272, 278 tobe repositioned in a manner similar to that described before for upperarm 66 and shown in FIGS. 4A-6A. The structural features of the upperarm sections that form interface 273I may be similar (e.g. matingsurfaces, mounting holes and mounting/locking fasteners) to the featuresdescribed before with respect to arm sections 72, 78. The drive section234 in the embodiment shown in FIG. 7, has drive motors 242, 246 thatare mounted to the arm assembly 266. In the embodiment shown, the drivemotors 242, 246 are mounted on the upper arm 266. Drive motor 242 powersshaft 250A that is fixedly connected to forearm 274. Rotation of shaft250A rotates forearm 274 about axis F1 at one elbow of the arm assembly.Drive motor 246 powers shaft 250C that is fixedly connected to forearm306. Rotation of shaft 250C rotates forearm 306 about axis E at theopposite elbow of the arm assembly. Motor 244 is located at the shoulderjoint of the arm assembly. Motor 244 powers drive shaft 250B that isfixedly connected to the upper arm 266 to rotate the upper arm aboutaxis of rotation D at the shoulder. Synchronizers 298, 324 respectivelyanchor the end effectors 238, 239 to the upper arm during rotation ofthe forearms 274, 306. Though the forearm motors 242, 244 are shown inthis embodiment as being located exterior to the frames of the upper armand corresponding forearms, in alternate embodiments the motors drivingthe forearms may be positioned in any other desirable manner, such asbeing housed within the envelope provided by the frame of the upper arm,or the frames of the forearm, or may be situated in the space betweenthe forearm and upper arm. In still other embodiments, the forearm drivemotors may be located within the frame of the upper arm, but having thedrive shaft offset from the forearm axis of rotation at the elbows.Accordingly, in this case a suitable transmission, such as for examplesimilar to transmissions 84, 116 in FIG. 2 would drivingly connect themotor output shafts with idler pulleys on the forearms. Extension andretraction of the arm assembly 266 of the apparatus 210 is accomplishedin a manner substantially similar to that described before with respectto apparatus 10. The forearm motors 242, 244 may be controlled by acontroller (similar to controller 11 in FIG. 1) so that forearm rotationis about 2 times rotation of the upper arm in this embodiment.

Referring again to FIG. 1, a substrate buffer 400 may be provided to thetransfer chamber P. The buffer may be positioned within the chamber, ormay communicate with the chamber through a suitable port allowing thetransfer apparatus (and 210) to place/pick substrates from the buffer400. The buffer 400 is located out of the working envelope of thetransport arm during operation. The drive of the apparatus may be usedto allow the transport to access the buffer.

Referring now to FIGS. 8-9, there is shown a substrate transportapparatus 300 of the present insertion incorporating features inaccordance with another exemplary embodiment. FIG. 8 shows the apparatus300 in an extended position, and FIG. 9 shows the apparatus fullyretracted to its register position. The transport apparatus 300 in thisexemplary embodiment is generally similar to apparatus 10 describedbefore and similarly features are similarly numbered. Similar toapparatus 10, apparatus 300 generally comprises a drive section 330 andmoveable arm assembly 336. Arm assembly 336 in the exemplary embodimenthas, what shall be referred to as a general one side scara armarrangement with two end effectors 338, 339. The arm assembly in thisembodiment has an upper arm 340 and two forearms 342, 344 descendingfrom a common end of the upper arm. The forearms 342, 344 areindependently joined to the same end of the upper arm by independentelbow joints 346A, 346B as will be described below. The arm assembly336, similar to arm assembly 360 of apparatus 10, is connected to thedrive section 330 at shoulder joint 335 (see FIG. 8), to rotate (in thedirection indicated by arrow in FIG. 8) about the shoulder axis ofrotation Z1 and extend/retract (in the direction indicated by arrow R inFIG. 8) the end effectors 338, 339 to the pick/place locations for thesubstrates S. In this embodiment, the upper arm 340 defines twodifferent effective upper arm lengths 340A, 340B and the forearms 342,344 are of different lengths corresponding to the respective effectiveupper arm lengths as will be described further below. The end effectors338, 339 carried respectively by the forearms 342, 344 may be ofsubstantially equivalent length. The arm assembly 336 may be operatedwith drive 330 so that the reach with either end effector 338, 339 issubstantially the same. The arm assembly 336 is also operable to providea minimum footprint, for corresponding to the small swing diameter ofthe arm and independent give reach of the arm, of the larger swingdiameter as will be described further below.

Referring now to FIG. 9, the transport apparatus 300 is shown located ina representative transport diameter P1 similar to transport chamber Pdescribed previously and shown in FIG. 1. The transport chamber P1 maybe an atmospheric chamber, where the environment in the chamber interiorcommunicates generally with an exterior atmosphere, or may be anisolatable chamber capable or having to interior space isolated from theexterior atmosphere. For example, the isolated chamber P1 may have aninsert gas atmosphere or the interior of the chamber may maintain avacuum. The transport apparatus 300 may be mounted or otherwisepositioned in the chamber P1 in substantially the same manner asapparatus 10 in chamber P (see FIG. 1).

Referring now also to FIG. 10, which shows a cross-section view of thetransport apparatus, drive section 334 may have an outer housing 334Hthat houses a co-axial shaft assembly 360, and three motors 362, 364,366. In an alternate embodiment, the drive section could have more orfewer than three motors. The drive shaft assembly 360 has three driveshafts 368 a, 368 b, and 368 c. In an alternate embodiment more or fewerthan three drive shafts could be provided. The first motor 362 comprisesa stator 378 a and a rotor 380 a connected to the inner shaft 368 a. Thesecond motor 364 comprises a stator 378 b and a rotor 380 b connected tothe middle shaft 368 b. The third motor 366 comprises a stator 378 c androtor 380 c connected to the outer shaft 368 c. The three stators 378 a,378 b, 378 c are stationary attached to the housing 334H at differentvertical heights or locations along the housing. In this embodiment thefirst stator 378 a is the bottom stator, the second stator 378 b is themiddle stator and the third stator 378 c is the top stator. Each statorgenerally comprises an electromagnetic coil. The three shafts 368 a, 368b, and 368 c are arranged as coaxial shafts coaxial with shoulder axisof rotation Z. The three rotors 380 a, 380 b, 380 c may comprisepermanent magnets, but may alternatively comprise a magnetic inductionrotor which does not have permanent magnets. Sleeves 363 are locatedbetween the rotor 380 and the stators 378 to allow the transportapparatus 300 to be useable in a vacuum environment with the drive shaftassembly 360 being located in a vacuum environment and the stators 378being located outside of the vacuum environment. However, the sleeves363 need not be provided if the (see FIG.) is only intended for use inan atmospheric environment.

The first shaft 368 a is the inner shaft and extends from the bottomstator 378 a. The inner shaft has the first rotor 380 a aligned with thebottom stator 378 a. The middle shaft 368 b extends upward from themiddle stator 378 b. The middle shaft has the second rotor 380 b alignedwith the second stator 378 b. The outer shaft 368 c extends upward fromthe top stator 378 c. The outer shaft has the third rotor 380 c alignedwith the upper stator 378 c. Various bearings are provided about theshafts 368 and the housing 334H to allow each shaft to be independentlyrotatable relative to each other and the housing 334H. Each shaft 368may be provided with a suitable position sensor to signal a controllersimilar to controller 11 (see FIG. 1) of the rotational position of theshafts 368 relative to each other and/or relative to the housing 334H.Any suitable sensor may be used, such as optical or induction.

As seen in FIG. 10, the upper arm 340 is position, using suitablebearings to allow for rotation of the upper arm about shoulder axis ofrotation Z; onto the casing 334H of the drive section 334. The upper arm340 may have a hollow frame or casing capable of housing drivetransmission 320, 310 and communication lines (not shown) connecting theend effectors to suitable sources of power (not shown) and controller 11(see FIG. 1). The frame 340F of the upper arm may be a member of unitaryconstruction or may be an assembly as desired. As shown in FIG. 10, theupper arm frame is fixedly connected as one end 340R to the outer shaft308C so that the shaft and upper arm 340 are rotated as a unit aboutaxis of rotation Z at the shoulder joint 335 of the scara arm 336. Inthis exemplary embodiment, the upper arm 340 supports tow independentshaft assemblies 375A, 375B. Shaft assemblies 375A, 375B are located atthe opposite end 340F of the upper arm frame from the shoulder end 340R.Shaft assemblies 375A, 375B each define an independent elbow joint 346A,346B for independently mounting the respective forearms 342, 344 to theupper arm 340. Shaft assembly 375A generally comprises a rotatable outershaft 374, stably held in suitable bearings for free rotation about axisof rotation Z; at elbow joint 346A. Shaft assembly 375A may alsocomprise an inner post 373, generally concentric with shaft 374, butfixed to the upper arm frame as shown in FIG. 10. Shaft assembly 375B,of elbow joint 346B, is substantially similar to assembly 375A, with anouter rotatable shaft 372 and a concentric inner post 373B fixed to theupper arm frame. The rotatable shaft 372 of elbow joint 346B isrotatable about axis of rotation Z1″.

As seen best in FIG. 8, the shaft assemblies 375A, 375B are located onthe upper arm 340 with a radial and angular offset. In this embodiment,shaft assembly 375A (for elbow 346A) is located radially closer to thecenter of the shoulder joint (defined by axis of rotation Z′) than theshaft assembly 375B for elbow assembly 346B. Thus, the radial length340A between the center of rotation of elbow joint 346A (defined by axisof rotation Z1′) and the center of rotation of the upper arm (i.e. axisof rotation Z′) is smaller than the corresponding radial length 340Bbetween the center of rotation of the second elbow joint 346B (definedby axis of rotation Z1″) and the center of rotation of the upper arm.Shaft assemblies 375A, 375 are also separated by an angular offset B asshown. As seen in FIG. 8, both shaft assemblies 375A, 375B arepositioned on one side of the axis of translation T (connecting wristjoints center of rotation Z2′, Z3′ and shoulder joint center of rotationZ′ and along which the end effectors are translated in direction R). Theshaft assembly 375A (or elbow joint 346A) closest to the axis oftranslation T has the shorter radial (length) 340A compared to theradial 340B of the outer shaft assembly 375B (or elbow joint 346B). Theupper arm, may thus be considered as having two effective upper armlengths (corresponding to radials 340A, 340B) located on one side of theaxis of translation T of the end effectors. Although, in this exemplaryembodiment, the frame 340F of the upper arm has been shown as being ofmonolithic shape to appear as but a single arm, in alternate embodimentsthe upper arm frame may have any other suitable shape for locating andsupporting the two offset shaft assemblies on one side of the axis oftranslation (for example, the frame of the upper arm may be bifurcatedto appear as two arms extending from the shoulder joint, similar toshoulder joint 335 to the independent elbow joints). As may be realized,the radial and angular offset may be established as desired to provide aminimum apparatus footprint, and the elbow joints 346A, 346B are shownin FIG. 8 with minimum separation.

Referring again to FIG. 10, forearm 342 is fixedly mounted to shaft 374to rotate as a unit with shaft 374 about axis of rotation Z1′ at elbowjoint 346A. The second forearm 344 is fixedly mounted to shaft 372 torotate as a unit with shaft 372 about axis of rotation Z1″ at elbowjoint 346B. As seen in FIG. 8, forearms 342, 344 each have differenteffective lengths (the effective forearm length is defined here as thedistance between the center of rotation Z1′, Z1″ at the elbow joint346B, 346A and the center of rotation Z′3, Z′2 at the wrist joint 338W,339W corresponding to the forearm 342, 344). In this embodiment, forearm342 is shorter than forearm 344. As may be realized from FIG. 8, theeffective length of each forearm 342, 344 is commensurate to the radiallength 340A, 340B to the corresponding elbow joint 346A, 346B joiningthe given forearm to the upper arm 340. Hence, in this embodiment theeffective length of the forearm 342 at elbow joint 346A is substantiallyequivalent to radial length 340A. Similarly, forearm 344 at elbow joint346B has an effective length substantially equal to the radial length340B. One forearm 344 is staggered vertically from the other to allowboth arms to be pivoted freely about the respective axis of rotationZ1′, Z1″ without interference with each other. In this embodiment, theouter and longer forearm 344 is located above the inner shorter forearm342. Sufficient standoff may be provided at shaft assembly 375B, toprovide the upper arm 344 with sufficient clearance relative to thelower arm 342.

Still referring to FIG. 8, each forearm 342, 344 carries an end effector338, 339 capable of rotating about corresponding axis of rotation Z3′,Z2′ relative to the forearm supporting it. In this embodiment, the endeffectors 338, 339 may have the same effector length, though inalternate embodiments, different length end effectors may be used. Inother alternate embodiments one or more of the end effectors may have abatch holding capability (such as by having a row of multiple substratesupports, see batch end effector BE in FIG. 12). In this embodiment, thetransport provided with each end effector 338, 339 is substantially thesame. Rotation of each forearm 342, 344 is independently powered bycorresponding drive shafts 368A, 368B of the drive section 334.

As seen in FIG. 10, in this embodiment the middle shaft 368 b isconnected to transmission to 320 in the upper arm 340, and the innershaft 368 a is connected to transmission 210 in the upper arm. The firsttransmission 320 in this embodiment may comprise a drive pulley 322, anidler pulley 324 and drive cables or belts 326. In alternateembodiments, any suitable transmission may be used. The drive pulley 322is fixedly mounted to the top of the middle shaft 368 b and is connectedby drive belt 326 to the idler pulley 324. The idler pulley 324 isfixedly mounted to shaft 372 of shaft assembly 375B connecting theforearm to the upper arm. The second transmission 310 in the upper armlink 340 may comprise a drive pulley 312, an idler pulley 314, and drivebelt or cables 316. Drive pulley 312 is fixedly mounted to the top ofinner shaft 368 a of coaxial shaft assembly 360 in drive section 334.The idler pulley 314 is fixedly mounted to shaft 374 of shaft assembly375A connecting the forearm 342 to the upper arm 340. Drive belt 316connects the drive pulley 312 to the idler pulley 314. The reductionratio between the idler and the drive pulleys 314, 312 of the secondtransmission 310, and between the idler and drive pulleys 324, 322 ofthe first transmission 320 in this embodiment is about 1:2, though inalternate embodiments the ratio between the idler and drive pulleys maybe as desired. The drive belts 316, 326 are configured to rotate therespective idler pulleys 314, 304 in the same direction as thecorresponding drive pulley 312, 322 (e.g. clockwise rotation of drivepulleys 320, 322 causes clockwise rotation of idler pulley 314, 322).

Rotation of the end effectors 338, 339 about the corresponding axis ofrotation Z3′, Z2′ is slaved to the upper arm 340 by synchronizers 396,408 shown in FIG. 10.

Forearm synchronizer 396 may be located within the forearm 342, and maycomprise drum 402, idler pulley 404, and connecting cable(s) or belt(s)406. Drum 402 is fixedly mounted to the stationary post 373A (fixed toupper arm 340). Idler pulley 404 is fixedly mounted to shaft 398pivotally connecting the end effector 338 to the forearm 342. Belt(s)406 connects the drum 402 to the idler 404 and are preferably configuredto have a general loop shape (not shown) so that rotation of the forearmlink 342 about axis Z1′ causes counter-rotation of the idler 404 aboutaxis Z3′. Drum 402 on fixed post 373A diameter to idler pulley 404,diameter ratio may be about 1:2. The aforementioned ratios of forearmsynchronizer 396 and of the second transmission 310 (see FIG. 10) causesthe end effector 338 to maintain a substantially straight line motionalong traverse axis T (see FIG. 8). Forearm synchronizing mechanism 408is located in forearm 344, and comprises drum 410, idler 412, andconnecting cable(s) or belt(s) 414. The driver 410 is fixedly mounted tothe top of fixed post 373B. Idler 412 is fixedly mounted to shaft 416which pivotally connects the end effector 339 to forearm link 344.Cable(s) 414 connect the drum 410 to idler 412 and are preferablyconfigured in a general loop shape (not shown), so that rotation of theforearm link 344 about axis Z1″ causes counter-rotation idler 412 aboutaxis Z2′. The diameter ratio between idler 412 and drum 410 ofsynchronizer 408 may be about 2:1. These ratios in combination with thereduction ratio of the first transmission 320 in the upper arm 340causes the end effector 339 to traverse in a substantially straight linealong traverse axis T when the scara arm 236 is extended or retracted.

As seen in FIG. 10, in this embodiment the end effectors 338, 339 arerespectively mounted on the corresponding forearms 342, 344 to beadjacent to the upper surfaces of the forearm. This allows both forearmsto pass through a vacuum slot valve (not shown) of the transport chamberP (see FIG. 8). In alternate embodiments, the end effectors may bemounted to the respective forearms to be located between the upper andlower forearms in a manner similar to end effectors 38, 39 shown inFIGS. 1-2. FIG. 10A shows the end effectors mounted on the forearms in aconfiguration in accordance with yet another exemplary embodiment. Theend effectors 338′, 339′ and forearms 342′, 344′ in this embodiment,except as described otherwise are substantially similar to the endeffector and forearms of apparatus 300 described before and shown inFIGS. 8-10, and similar features are similarly numbered. End effectors338′, 339′ are mounted, as shown in FIG. 10A, to the bottoms of thecorresponding forearms 342′, 344′. End effector 339′, may have anextension portion 339′E as shown, allowing the horizontal blade 339′B ofend effector 339′ (carried by upper forearm 344′) to be positioned inclose vertical proximity to the end effector 338′ (carried by the lowerforearm 342′). As may be realized from FIGS. 8 and 10A, the differentiallength of the forearms 342, 3444, 342′, 344′ in this embodiment allowthe apparatus 300 to execute a first swap movement without mounting oneof the end effectors on a conventional bridge in order to allow the endeffectors and forearms to move past one another during swap motion. Inthis embodiment, the different length forearms 342, 344, 342′, 344′ andoffset of the elbow joints 346A, 346B, where the forearms arerespectively rotated, suffice to enable the forearms and correspondingend effectors 338, 339, 338′, 339 to move freely past one another duringswap movement as will be described further below.

Extension and retraction of arm assembly 336 may be effected in asimilar manner to that described before with respect to arm assembly 36shown in FIGS. 1-2. To extend end effector 338 (for example from itsregister position shown in FIG. 9), the upper arm 340 is rotatedclockwise about axis Z′ (by drive shaft 368C see FIG. 10). The forearm342, supporting end effector 338 is rotated counter clockwise about axisZ1′ (by drive shaft 368A), and synchronizer 396 maintains the endeffector 338 aligned true to the axis of translation T (see FIG. 8). Thesecond forearm 344, and corresponding end effector 339, forearm 344 mayremain in its retracted position (see FIG. 9) relative to the upper arm.Referring to FIG. 8, reference 339W′ indicates the location of the endeffector wrist 339W with the end effector 339 in its retracted positionand when the upper is moved so that end effector 338 is extended. Toretract end effector 338, the forearm 342 may be rotated now clockwiseabout axis Z1′. Line 342R represents the path of the outermost portionof the forearm 342 as it is rotated about axis Z1′ towards its retractedposition, while the upper arm 340 remains in its extended position inpreparation for extending end effector 339. As seen in FIG. 8, and alsoin FIG. 9, the forearm 342 moving end effector 338 to its retractedposition, clears the wrist 339W of end effector 339 allowing theforearms and corresponding end effectors to move freely past each otherto effect the swap movement without a bridge for the end effector. Endeffector 339 is extended and retracted by rotating the forearm 3434respectively counterclockwise and clockwise about axis Z1″ with driveshaft 368B (see FIG. 10). As seen in FIG. 9, the longer forearm 344 isunder rotated (compared to the shorter forearm 342) during retraction,and hence extension, so that the register position of end effector 339is located to minimize the footprint of apparatus 300.

Transport apparatus 300 has a simplified bearing and communication linefeed through compared with conventional transport apparatus withmultiple forearms mounted on a common (concentric) elbow joint. FIG. 11illustrates an example of the feed arrangement of communication lines338L, 339L, respectively fed to end effectors 338, 339, through theupper arm 340, elbow joints 346A, 346B and forearms 342, 344 oftransport apparatus 300. The feed arrangement shown eliminates the needfor a vacuum lip seal and slip rings between forearms. This results in asimpler arm with less wear components that is more reliable and easierto fabricate than conventional device.

It should be understood that the foregoing description is onlyillustrative of the invention. Various alternatives and modificationscan be devised by those skilled in the art without departing from theinvention. Accordingly, the present invention is intended to embrace allsuch alternatives, modifications and variances which fall within thescope of the appended claims.

What is claimed is:
 1. A substrate transport apparatus comprising: asubstantially rigid upper arm having a first upper arm section and asecond upper arm section coupled to each other at a common axis ofrotation by a releasable coupling to form the substantially rigid upperarm having opposing ends; a first forearm rotatably coupled to a firstone of the opposing ends; a second forearm rotatably coupled to a secondone of the opposing ends; and at least one end effector rotatablycoupled to each of the first forearm and second forearm, each of the atleast one end effector being configured to hold at least one substrate;wherein the releasable coupling is configured to change a size of aninclusive angle between the first upper arm section and the second upperarm section, where the inclusive angle is fixed for transportingsubstrates.
 2. The substrate transport apparatus of claim 1, wherein alength of the at least one end effector corresponds to the inclusiveangle.
 3. The substrate transport apparatus of claim 1, wherein thereleasable coupling comprises fixing holes disposed in mating surfacesof each of the first upper arm section and second upper arm section, thefixing holes being configured to provide incremental adjustment of theinclusive angle.
 4. The substrate transport apparatus of claim 1,wherein the releasable coupling defines the common axis of rotation. 5.The substrate transport apparatus of claim 1, wherein the first upperarm section and the second arm section extend on opposite sides of thecommon axis of rotation.
 6. The substrate transport apparatus of claim1, further comprising a drive section operably coupled to at least theupper arm and each of the first forearm and the second forearm.
 7. Thesubstrate transport apparatus of claim 6, wherein the drive sectiondefines an axis of rotation substantially collinear with the common axisof rotation, the upper arm being mounted to the drive section to rotaterelative to the drive section about the common axis of rotation.
 8. Thesubstrate transport apparatus of claim 6, wherein the drive sectionincludes three drive axes for rotating respective ones of the upper arm,the first forearm and the second forearm.
 9. A substrate transportapparatus comprising: a substantially rigid upper arm having a firstupper arm section and a second upper arm section coupled to each otherat a common axis of rotation by a releasable coupling to form thesubstantially rigid upper arm having opposing ends; a first forearmrotatably coupled to a first one of the opposing ends at a first elbowaxis; a second forearm rotatably coupled to a second one of the opposingends at a second elbow axis; and at least one end effector rotatablycoupled to each of the first forearm and second forearm, each of the atleast one end effector being configured to hold at least one substrate;wherein the releasable coupling is configured to change a distancebetween the first elbow axis and the second elbow axis, where thedistance between the first elbow axis and the second elbow axis is fixedfor transporting substrates.
 10. The substrate transport apparatus ofclaim 9, wherein a length of the at least one end effector correspondsto the distance between the first elbow axis and the second elbow axis.11. The substrate transport apparatus of claim 9, wherein the releasablecoupling comprises fixing holes disposed in mating surfaces of each ofthe first upper arm section and second upper arm section, the fixingholes being configured to provide incremental adjustment of theinclusive angle.
 12. The substrate transport apparatus of claim 9,wherein the releasable coupling defines the common axis of rotation. 13.The substrate transport apparatus of claim 9, wherein the first upperarm section and the second arm section extend on opposite sides of thecommon axis of rotation.
 14. The substrate transport apparatus of claim9, further comprising a drive section operably coupled to at least theupper arm and each of the first forearm and the second forearm.
 15. Thesubstrate transport apparatus of claim 14, wherein the drive sectiondefines an axis of rotation substantially collinear with the common axisof rotation, the upper arm being mounted to the drive section to rotaterelative to the drive section about the common axis of rotation.
 16. Thesubstrate transport apparatus of claim 14, wherein the drive sectionincludes three drive axes for rotating respective ones of the upper arm,the first forearm and the second forearm.